Flotation feed control



H. L. MEAD Erm.

FLOTATION FEED CONTROL Filed nec. 27, 1939 septu 29, 1942.

Patented Sept. 29, 1942 FLOTATION FEED CONTROL Harry L. Mead and Ernest J. Maust, Brewster,

Fla., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application December 27, 1939, Serial No. 311,092 1 Claim.. (Cl. 209-3) The present invention relates to deslimed flota` tion feed control and more particularly it relates to a method and apparatus for elevating and regulating the quantity of a deslimed non-metallic flotation feed for introductioninto a flotation circuit.

The problem of controlling the tonnage vof deslimed flotation feed introduced into a flotation circuit has been a serious one and this is especially true with deslimed non-metallic flotation feed such as phosphate sand flotation feed. Deslimed phosphate sand flotation feed is usually stored in feed storage or dewatering tanks from which it is conveyed to a flotation machine or string of flotation machines for recovery of B. P. L. These storage tanks are equipped with a discharge valve in the bottom through which the flotation feed is fed tothe flotation circuit.' One of the more common types of discharge valve controls is of the rubber pinch clamp type, which an operator regulates to control l'the tonnage of flotation feed discharged from the tank. With this and the other type valves in common use, careful supervision by the operator is required to hold the feed tonnage steady and he must attempt to compensate for the lag in -correction lbetw-een tonnage of feed and reagents, resulting in loss of efliciency and production.

Still another disadvantage of the prior art resides in the location of the feed ltanks relative to flotation machines. The feed tanks are sometimes located on a floor directly above the flotation machines in' which case the pinch clamp or similar controlled discharge valves are opened and the flotation feed flows by gravity to the flotation circuit. Not only is the tonnage of the flotation feed difficult to control by this method but there is considerable expense required in constructing the plant on different levels and also in elevating the feed to the storage tanks. When the feed tanks and flotation machines are located on the same floor level, the feed after discharge from the pinch clamp controlled valve must be elevated for introduction into the flotation machines. While this plant plan eliminates the increased -construction expense due to location ofv the feed tanks and flotation machines on different levels it does not simplify or solve the problem of controlling the tonnage of flotation feed and also introduces another problem, namely elevating the flotation feed to flotation machine level. The flotation feed in this case is usually elevated to flotation machine level by means of conveyors or rotary force pumps, neither of which CII provide any means of control of the feed tonnage,

and are expensive to maintain due to excessive Wear from the abrasive constituent of the phosphate sands.

According to the present invention an im-v proved method and apparatus for controlling the tonnage of deslimed non-metallic flotation feed and elevating to flotation machine level is provided.

It is recognized in the pumping art that diaphragm pumps are not only economical in power and maintenance cost 4but can also be easily regulated to control the quantity of fluid which passes through the system. Heretofore diaphragm suction pumps have been employed for the pumping of corrosive, abrasive, granular or thick liquids, slimes or heavy sludges, slurries, etc. in which the solid particles if present were of fine or colloidal size to produce more or less stable suspensions. In the yore dressing art diaphragm pumps have been employed to elevate and control slimes, and

slimy ground ore pulps from the bottom of a thicker or storage tank. The slimy or colloidal substances in the 'past have been considered essential -constituents of ore materials that were to be elevated by means of diaphragm pumps and it was not therefore thought that diaphragm suction pumps could be used to elevate deslimed flotation feeds. We have discovered a novel arrangement and means whereby deslimed sands can -be elevated by an ordinary diaphragm pump system. We have found that by the addition of Water to the suction line of a-diaphragmpump a't the point of emergence of deslimed flotation feed sands from a tank into the suction line, the deslimed sands can be elevated by the action of the diaphragm pump in spite of the normal tendency of such material to sand up or clog the pipe line.

The many advantages of the present invention will be readily apparent to those skilledf in the art of handling deslimed flotation feeds and especially in deslimed non-metallic flotation feeds such as those of the phosphate field. It permits the most economical method of plant construction since the feed storage tanks and otation machines can be located on the same floor level. Also the quantity or tonnage of feed fed to the flotation machines can be accurately controlled by simply increasing or decreasing the length of the stroke of the diaphragm/pump or the number of. strokes per minute and the control is applicable over a Wide range which permits the same apparatus to gbe employed in the handling of various ore materials. 'I'his accurate control of the tonnage not only results in obtaining a maximum recovery of values with a minimum-reagent cost but also results in a great saving of time and labor. It is also an advantage of the present invention that the same apparatus elevates and controls the tonnage of flotation feed, whereas inl the prior art two separate and distinct operations were required; one to discharge and regulate the tonnage of feed from the storage tanks and the second step of elevating the feed to flotation level.

The accompanying drawing which is a diagrammatic elevation serves to further illustrate the novel features ofthe present invention.

The apparatus comprises an ordinary flotation feed storage tank II with an inlet*I 2 for the deslimed feed and an overflow outlet 3 near the top, and a discharge opening 4 in the bottom of the tank which opens into the suction line 5 of a diaphragm suction pump 6, said discharge opening also having a hydraulic water inlet 1 near the point at which the suction line and discharge opening merge.

In operation the deslimed flotation feed sand is fed into the tank whereupon the deslimed sands settle to approximately 75% solids depending on the type of ore, and the excess water from the dewatered feed overflows through the overflow outlet. The diaphragm suction pump located on a level approximately equal to that of the top of the feed tank is started to operate, the valve in the lower portion of the suction line is opened whereupon the deslimed sand enters the suction pipe while being thoroughly intermixed with the hydraulic water at the point of emergence into the suction line whereupon the deslimed sand and water are lifted by the Asuction action of the diaphragm pump and. fed into a mixer containing the necessary flotation reagents and thence to a flotation machine. The flotation feed tonnage is regulated by adjusting the length of the stroke of the diaphragm pump or varying the speed of the pump, that is to say, the number of strokes per minute.

The following data illustrates the diaphragm pump performance in elevating deslimed flotation feed in which all the variables are eliminated except the amount of water added to the suction line at the bottom of the tank of deslimed sand. The flotation feed is sucli .that it cannot be elevated by a diaphragm suction pump when operated in the'normal manner.

The above data shows that there is very little variation in the tonnage of sand pumped for different amounts `of water added to the suction line, except near the point of the minimum amount required before pump failure. There is, however, av

direct relation between the amount of water added and the percent solids in the pump discharge, which is important in regulating .the percent solids in the flotation machine.

The amount of water above the minimum is not critical and does not require that it be accurately controlled since there is very little difference between the net results of the pump performance, as the above data shows, between the addition of 214 and 131 gallons of water per minute.

The minimum amount of water required will vary with different ore materials. In this particular case the minimum amount of water added was slightly over 50 gallons per minutev or such that the percent solids in the discharge was approximately 66%.

The following data illustrates how a variable tonnage is obtained by varying the length of the stroke of the diaphragm pump. The pump employed in these tests is an ordinary six inch duplex diaphragm pump. The tests were conducted on both a coarse deslimed phosphate sand feed screen analysis showing 96% solids ranging in particle size from -20 to +100) and a fine feed (screen analysis showing 96% solids ranging in size from to +200).

COARSE FEED Gallons water added per minute Pump discharg, per cen i solids 30 'iest Stroke .8&5

noch

Sms

use

The above data shows that the quantityor .tonnage of deslimed flotation feed elevated by our improved method can be controlled by varying the length of the stroke of the diaphragm pump. The tonnage can be further regulated by other variables, such as the number of strokes per minute of the pump, the size of the pump, the amount of water introduced into the suction line, etc.

What we claim is:

A' method of controlling an elevating deslimed phosphate rock flotation feed which comprises introducing a deslimed phosphate flotation feed containing about '75% solids into the suction line of a diaphragm pump while simultaneously and continuously introducing into said suction line an amount of water sufficient to reduce the solids content in the suction line to from about to not more than about 65% solids, elevating and discharging the diluted flotation feed through the diaphragm pump.

HARRY L. MEAD. ERNEST J. MAUST. 

